Stopping Distances (Edexcel GCSE Physics: Combined Science)

Write down an equation which relates thinking distance, braking distance and stopping distance. 

A truck driver is travelling along a road at 25 m/s when they spot red traffic lights 200 m ahead.

The truck driver has a reaction time of 0.84 s, however they are tired so their reaction time is twice as long. 

Calculate the truck driver's thinking distance.

Figure 1

25 m/s = 90 km/h. The lorry's brakes can produce a deceleration of 3.5 m/s².

Estimate the stopping distance of the lorry.

When the truck fully applies its brakes, it comes to rest only 5 m before the red light. 

Suggest two reasons why this may have happened.

A council introduces 20 miles per hour (mph) speed limit in a particular region of a city.

A member of the council states that drivers can react faster at 20 mph than they can at 30 mph.

Explain what is wrong with the councillor's statement.

Figure 1

Describe how thinking distance varies with increasing speed.

Use data from the graph in your answer.

A scientist uses different drivers to test the stopping distances of the same car.

Figure 1 shows the results.

Figure 1

Most of the drivers tested the car on a dry day, on a level road.

State which driver tested the car on a wet road.

State which driver has the shortest reaction time.

Calculate their reaction time, giving your answer to 1 significant figure.

Driver 2 travels at 24 m/s on the road. The thinking distance is 20m and the braking distance is 36 m.

Calculate the deceleration of the car.

You may assume the braking force is uniformly applied.